Serve hot chocolate with sugar cubes, chocolate chunks, candy-coated chocolate pieces, and biscotti.
Stir together boiling water and chocolate syrup in a medium saucepan; add milk, stirring until blended. Cook over medium heat 6 to 8 minutes or until thoroughly heated. Remove from heat, and stir in liqueur. Garnish, if desired.
Note: For testing purposes only, we used Frangelico for hazelnut liqueur.